Photolithography is commonly used during formation of integrated circuits on semiconductor wafers. More specifically, a form of radiant energy is passed through a radiation-patterning tool and onto a radiation-sensitive material associated with a semiconductor wafer. The radiant energy can be referred to as actinic energy, and will typically be light in the ultraviolet (UV) range or visible range. The radiation-sensitive material is a photo-imageable material, such as, for example, photoresist.
The radiation-patterning tool can be referred to as a photomask or a reticle. The term “photomask” traditionally is understood to refer to masks which define a pattern for an entirety of a wafer, and the term “reticle” is traditionally understood to refer to a patterning tool which defines a pattern for only a portion of a wafer. However, the terms “photomask” (or more generally “mask”) and “reticle” are frequently used interchangeably in modern parlance, so that either term can refer to a radiation-patterning tool that encompasses either a portion or an entirety of a wafer. For purposes of interpreting this disclosure and the claims that follow, the terms “reticle” and “photomask” are utilized with their traditional meanings.
Advances in semiconductor integrated circuit performance have typically been accompanied by a simultaneous decrease in integrated circuit device dimensions and a decrease in the dimensions of conductor elements which connect those integrated circuit devices. The demand for ever smaller integrated circuit devices brings with it demands for ever-decreasing dimensions of structural elements, and ever-increasing requirements for precision and accuracy in radiation patterning. Accordingly, it is desired to develop improved tools and processes for radiation patterning.